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1.
Titan's haze consists of long chain polymers of pure and N-mixed hydrocarbons (Coustenis et al., 1989, Icarus 80, 54-76, 1991, Icarus 89, 152-167). These polymers have regularly alternating (i.e., conjugated) double/single and triple/single bonds, which open either spontaneously (free aging) or under the action of some external factors (forced aging), the latter being very diverse, e.g., charging, photolysis, radiolysis, thermolysis, chemical effect of environment, etc. An essential of free aging was examined previously (Dimitrov and Bar-Nun, 2002, Icarus 156, 530-538). The main distinction between free and any forced aging is that both of them possess the same thermodynamics while different kinetics, the forced aging in any case being faster, proceeding in different pathways than the free aging. The more extensive is the list of the external effects and the more intensive they are, the faster and more variably the forced aging proceeds. In this paper we quantified the kinetics of forced aging, considering charging of Titan's aerosol population. It was found that forced aging proceeds approximately hundred times faster as compared to the free aging. Various physico-chemical properties of Titan's aerosol material, including coagulation coefficients, depending on particle size and medium conditions, were defined. The comparison of the aging rate, rate of sedimentation and rate of the particle increase proves that Titan's aerosol domain can be subdivided conditionally into two big subdomains. The upper one contains minor portion (<5%) of the total aerosol bulk, unannealed aerosol particles being fine and sticky. The lower subdomain contains the major portion (>95%) of aerosol bulk, which is completely aged, coarsely dispersed particles. We established the border between these subdomains at the altitude Z∼620 km. 相似文献
2.
The interaction of corotating iogenic plasma with the surface of Europa in light of recent ice sputtering, experimental results, and published Voyager data has been examined. It has been found that the residual atmosphere of Europa is made up of sputtered molecular oxygen and is exospheric from the surface outwards. It was also found that if sputtering, redistribution, and escape are considered and the sulfur dioxide/water mixing ratio is held constant over a UV observing depth, the observed sulfur dioxide density on the trailing hemisphere lends support to the hypothesis that liquid water from the interior of Europa is boiling out and being deposited as a frost layer on the surface at the rate of about 0.04 μm/year. 相似文献
3.
We suggest that the regions of smooth terrain which were observed on Comet 9P/Tempel 1 by the Deep Impact spacecraft were formed by blowing ice grains in an outburst of gas from the comet interior. When gas is released from 10 to 20 m deep layers which were heated to 135 K, it is released quiescently onto the surface by individual conduits. If large amounts of gas are released, the drainage system cannot release them fast enough and wider interconnected channels are formed, leading to sudden outburst of gas. Instability triggering a sudden shift of flow is well known in subglacial drainage of water. The ballistic trajectory of the ice particles reach a distance of 3 km in the atmosphereless comet, whose gravity is 0.034 cm s−1, if ejected at an angle of 45° at a speed of 95 cm s−1. This speed is close to the speeds measured in laboratory experiments: 167, 140×sini and 167 cm s−1, for particles of 0.3, 1000 and 14-650 μm, respectively. Blowing of ice grains can overcome the 1650 m long horizontal section of smooth terrain i1 (Fig. 1), whereas simple flow of material downhill would stop close to the foot of the hill. The ice particles at the end of their trajectory have a horizontal velocity component and this low velocity ballistic sedimentation would lead to formation of lineaments on the smooth terrain, like in solid-particulate volcanic eruptions. 相似文献
4.
Iron-rich veins are associated with tectonic features in Israel and adjacent lands. These iron-bearing veins within otherwise metal-poor sedimentary rocks are commonly accompanied by significant enrichments of other metals such as Mo, Zn, As, V, Ni, Mn, Pb and U. Restriction of these mineralized veins to well delineated tectonic zones suggests the need for re-evaluation of the mineral resource potential of the area. A conceptual geochemical model to guide exploration is provided. 相似文献
5.
The detection of CH4 in the martian atmosphere, at a mixing ratio of about 10 ppb, prompted Krasnopolsky et al. [Krasnopolsky, V.A., Maillard, J.P., Owen, T.C., 2004. Icarus 172, 537-547] and Krasnopolsky [Krasnopolsky, V.A., 2006. Icarus 180, 359-367] to propose that the CH4 is of biogenic origin. Bar-Nun and Dimitrov [Bar-Nun, A., Dimitrov, V., 2006. Icarus 181, 320-322] proposed that CH4 can be formed in the martian atmosphere by photolysis of H2O in the presence of CO. We based our arguments on a clear demonstration that CH4 is formed in our experiments, and on thermodynamic equilibrium calculations, which show that CH4 formation is favored even in the presence of oxygen at a mixing ratio 1.3×10−3, as observed on Mars. In the present comment, Krasnopolsky [Krasnopolsky, V.A., 2007. Icarus, in press (this issue)] presents his arguments against the suggestion of Bar-Nun and Dimitrov [Bar-Nun, A., Dimitrov, V., 2006. Icarus 181, 320-322], based on the effect of O2 on CH4 formation, the absence of kinetic pathways for CH4 formation and on the inadequacy of thermodynamic equilibrium calculations to describe the martian atmosphere. In this rebuttal we demonstrate that experiments with molecular oxygen at a ratio of O2/CO2=(8.9-17)×10−3, exceeding the martian ratio, still form CH4. Thermodynamic equilibrium calculations replicate the experimental CH4 mixing ratio to within a factor of 1.9 and demonstrate that CH4 production is favored in the martian atmosphere, which is obviously not in thermodynamic equilibrium. Consequently, we do not find the presence of methane to be a sign of biological activity on Mars. 相似文献
6.
Unlined rock caverns for oil storage are very common in Sweden. Most of them are excavated in hard rocks (compact, non-carbonate, non-volcanic rocks). The fundamental idea of underground oil storage is that the rock caverns are located below the natural ground water level. Hereby the ground water keeps the oil inside the caverns and prevents products migration.
During the excavating period the water seeping through the fractures of a cavern is pumped up to avoid flooding. This discharge causes a local drop in the ground-water level around the cavern and a cone of depression develops.
A local study of the development of such a cone of depression has been made by means of a network of observation holes around the cavern. On enlargement of an oil storage (by constructing new caverns close to the old ones), the cone of depression moves according to the progress of the new excavations. This process has been studied and described in two cases.
Underground storages in Sweden are very often closely spaced in order to use common facilities such as entrance tunnel, pumping station, housing etc. Therefore an artificial ground-water divide sometimes must be arranged between different caverns in order to prevent products migration. This paper describes how such an artificial recharge of water between some caverns is made. The control of its effectiveness is shown as well as the method for sealing off undesirable leakage. 相似文献
7.
We suggest that the methane observed on Mars can be formed by photolysis of water vapor in the presence of CO, in addition to possible geological sources, rather than biologically. 相似文献
8.
The Judean Mountains' anticlinorium, Israel, a part of the Syrian Arc fold system, underwent several phases of compressional folding, uplift and faulting in post-Turonian through Quaternary times. This study emphasizes the earliest tectonic phase of earIy Late Coniacian age. Ostracode biozonation clearly indicates the duration and extension of Senonian sedimentation and timing of onlap over the evolving Judean Mountains' structure. 相似文献
9.
Epigenetic manganese mineralization occurs within Cretaceous carbonate strata of Israel. This mineralization is structurally controlled. In southern Israel, manganese- and iron-bearing waters rising along fault zones precipitated these metals as different redox conditions were encountered. The manganese and associated trace-metals are believed to be leached from magmatic bodies by corrosive deep-seated brines in southern Israel and circulating meteoric waters in northern Israel. 相似文献
10.
Akiva Bar-Nun 《Earth, Moon, and Planets》2009,105(1):55-56